An amplifier is an element used in many communication circuit configurations. For example, amplifiers are used in mixers, filters, multipliers, and oscillators. An input signal is applied to an amplifier and amplified by the amplifier. Parameters that affect the performance of an amplifier are gain, noise, and power dissipation.
Intermediate Frequency (IF) amplifiers are used in receiver circuits for receiving modulated Radio Frequency (RF) signals in wireless communication applications such as cellular telephones or cordless telephones. The received modulated RF signal is translated to an Intermediate Frequency (IF) signal for demodulation. An IF amplifier amplifies the IF signal and provides the amplified IF signal to other components of the receiver circuit.
One prior art IF amplifier includes a voltage gain amplifier coupled between two ceramic filters. It is desirable to have an IF amplifier with low noise voltage, low power consumption, and a minimum number of external components. In addition, it is desirable for the input and output impedances of the IF amplifier to match the impedances of the ceramic filters. A prior art IF amplifier includes separate source and load matching resistors for matching the impedances of the two ceramic filters. However, the separate source and load resistors increase the power dissipation of the IF amplifier.
Accordingly, it would be advantageous to have an amplifier circuit for amplifying IF signals and method for reducing noise in the amplifier circuit. It would be of further advantage for the amplifier circuit to have low power consumption and a minimum number of external components.